A multi-layer printed circuit board, which has different thickness in each portion, is known as a rigid-flexible printed circuit board. The rigid-flexible printed circuit board is composed of a rigid board portion and a flexible board portion. For example, the rigid board portion is composed from a five-layer printed circuit board, and is used for mounting high-density printed circuit. The flexible board portion is composed, for example, from a four-layer printed circuit board, and is flexible. The flexible board portion is made of polyimide resin, and the rigid board portion is made of epoxy resin. In a related art, the rigid board portion and the flexible board portion are formed individually. Then, the rigid board portion and the flexible board portion are bonded and electrically connected to each other so that the rigid-flexible printed circuit board is formed. This method of manufacturing the rigid-flexible printed circuit board according to the related art is very complicated, and the structure of the rigid-flexible printed circuit board is also complicated.